Abstract : In this paper, we discuss a quantized feedback based diagonal precoder for 4 × 1 multiple-input single-output (MISO) system employing real orthogonal space-time block code (ROSTBC). Precoding improves the coding gain of the MISO system by exploiting channel state information at transmitter. ROSTBC helps in achieving full spatial diversity, full rate, and symbol-wise decoding for arbitrary number of transmit antennas in MISO system. An accurate closed-form expression of the symbol error rate (SER) of considered MISO system is derived with erroneous feedback by using the order statistics. Optimized transmit weights are obtained by minimizing the average SER of the precoding scheme. Simulated and analytical results show that the proposed scheme achieves significant improvement over MISO system employing ROSTBC only. Further, the scheme remains insensitive to the feedback errors.